March 19, 2011 (by Lieven Dewitte) - The entire fleet of F-35 Lightning II jets has been grounded pending an investigation into what caused a dual generator failure and an oil leak during flight tests of AF-04 at Edwards Air Force Base.
AF-4 on its first flight on December 30th, 2010. Pilot was Lockheed Martin test pilot Bill 'Gigs' Gigliotti.
The F-35A returned safely to base, but further test flights are being delayed while engineers figure out the cause of the problem.
The aircraft in question arrived at Edwards in late January and was the fifth F-35A conventional take-off and landing aircraft to ferry there for testing.
The grounding appears to have occurred because of the potential for loss of control posed by such a combination.
Unlike previous fighter jets, the F-35's flight control surfaces are controlled by electro-hydrostatic actuators. If they don't have power then the pilot can lose control. In this case, the back-up power system — the Integrated Power Package which also serves as the starter and air conditioner — kicked in as designed, allowing the pilot to return to base.
Kent noted that the F-35 has now flown 657 flights and this appears to be the first time a flight has encountered this problem. "Once the cause is known, the appropriate repairs and improvements will be made before flight operations resume," he said.
The incident occurred at Edwards Air Force Base, Calif., which is the main Air Force flight test facility, on aircraft AF-4, the fourth Air Force test plane. There are 10 F-35 test aircraft operating at Edwards and Naval Air Station Patuxent River, Md.